Update RFOverlayScrollView.m

-Added a method to restrict the scroller origin.x and height so that it doesn't overlap with NSTableHeaderViews
Update RFOverlayScrollView.h

-Added a method to restrict the scroller origin.x and height so that it doesn't overlap with NSTableHeaderViews
Merge pull request #1 from bertrand-caron/master

RFOverlayScrollView